Summary: @philkuz pointed out that the intention of ST_UNSPECIFIED was to catch bugs where the semantic type wasn't set properly. This diff changes the system to treat ST_NONE as the default semantic type and catch all for inference rules. This surfaced a bug where the Metadata service wasn't correctly propagating Semantic type information from stirling (even though this information doesn't exist in stirling yet, it wasn't correctly propagating the ST_NONEs).

Test Plan: Checked that all output columns in the UI now have sem type ST_NONE and not ST_UNSPECIFIED.

Reviewers: philkuz, nserrino, #engineering

Reviewed By: nserrino, #engineering

Subscribers: philkuz

Differential Revision: https://phab.corp.pixielabs.ai/D5308

GitOrigin-RevId: 691b725a74819c1b9a7097bae208ba19fd12116a